Fire prevention system



April 21, m J. Q -r' ET AL FIRE PREVENTION SYSTEM Filed Oct. 23. 1967 2Sheets-Sheet l INVENTORS DONALD J. QUANT LARRY M. WOOD ATTORNEYS o. J.QuANT ET AL FIRE PREVENTION SYSTEM April 21, 1910 2 Sheets-Sheet 2 FiledOct. 23, 1967 Q INVENTQRS DONALD J. QUANT LARRY M. WOOD '4 TTO/PNE vsUnited States Patent 3,507,333 FIRE PREVENTION SYSTEM Donald J. Quantand Larry M. Wood, Rochester, N.Y.,

assignors to Xerox Corporation, Rochester, N.Y., a

corporation of New York Filed Oct. 23, 1967, Ser. No. 677,159 Int. Cl.A62c 3/00 US. Cl. 1692 7 Claims ABSTRACT OF THE DISCLOSURE Fire controlapparatus for use in xerographic fusing zones. The apparatus includes anultraviolet detection tube positioned in the area to be sensed forflames. It is electrically coupled to a valve to control the flow offire extinguishing CO into the area being sensed. The electric circuitacts to release a pulse of CO upon the sensing of a flame by thedetecting tube. After the termination of the pulsed flow of CO thecircuit returns to its original state for a second flame sensing toallow supplemental pulsations and sensings until the flame isextinguished.

This invention relates to fire control apparatus, and, in particular, toapparatus for the detecting and extinguishing of fires in areas such asxero graphic fusers.

More specifically, this invention relates to apparatus for detecting thepresence of a flame at a xerographic fusing station and forextinguishing the flame with the required number of pulses of fireextinguishing fluid to put out the flame.

In the xerographic process a plate comprising a layer of photoconductivematerial on a conductive backing is given a uniform electric charge overits surface and then exposed to the subject matter to be reproduced bvarious projection techniques. This exposure discharges the plate inaccordance with the light intensity reaching it thereby creating anelectrostatic latent image on or in the plate.

Development of the image is effected by developers which comprise, ingeneral, a mixture of suitable resin based powder, hereinafter referredto as toner, and a carrier material which functions to carry and togenerate triboelectric charges on the toner. The function of the carriermaterial is to provide mechanical control of the toner, or to carry thetoner to an image surface, and simultaneously provide almost completehomogeneity of charge polarity. In the development of the image, tonerpowder is brought into surface contact with the photoconductive layerand is held thereon electrostatically in a pattern corresponding to theelectrostatic latent image. Thereafter, the developed xerographic imagemay be transferred to a support material to which it may be fixed by anysuitable means.

As the science of xerography has progressed, faster automaticxerographic reproducing machines have been developed, thus necessitatingimproved fixing apparatus cap able of fixing the toner powder image tothe support material at a rate compatible with the higher speedmachines. In fixing the toner powder to the support material it isdesired to obtain the highest possible quality of reproduction from theoriginal document. One such fixing apparatus is disclosed in copendingapplication Ser. No. 585,971 filed Oct. 11, 1966 in the names of GilbertA. Aser et al. For convenience of illustration the invention of thisapplication will be described with reference to its use therein,although it is not to be limited thereto.

In the apparatus disclosed in the above cited copending application, ithas been found desirable that a sheet of support material passingthrough the fixing apparatus be closely sensed to quickly detect thepresence of flames caused by the high temperature of the fuser acting onthe "ice toner image and backing sheet. It is also essential that anydetected flame be quickly extinguished before it damages the fusingelements of the xerographic reproducing machine generally.

Conventional fire sensing apparatus is insuflicient for the purposes ofthe instant application. For example, a photocell could not be used dueto the incandescency of the radiant energy creating mechanisms of thexerographic fuser. A thermistor also could not be used due to the hightemperature at which the fuser normally operates. Furthermore,conventional systems have insuflicientl fast response times for thepurposes needed in the instant system.

In the same manner, a flame detector responsive to actuate an unlimitedsupply of fire extinguishing fluid is undesirable. This is becauseexcess fluid such as CO would contaminate the area and require acleaning after each fire detection.

The present invention is in flame control apparatus including anultraviolet sensor capable of energizing a circuit and thus pulsating asmall amount of fire extinguishing fluid upon the detection of a flame.The system is self-capable of returning to its original state after thepulsation for resensing and repulsing of the fluid until the flame isextinguished. No excess fire extinguishing fluid need be used beyondthat needed for extinguishing the flame. Consequently, the apparatus ofthe instant invention is economical and clean in addition to beingdependable and quick.

It is, therefore, an object of the instant invention to extinguishflames in an area such as a xerographic fuser.

It is a further object of the instant invention to sense an area for thepresence of a flame and to extinguish any flame sensed in the area.

It is a further object of the instant invention to project a pulse offire extinguishing fluid into an area being sensed for flames.

It is a further object of the instant invention to project a pulse offire extinguishing fluid into an area being sensed for flames and tocontinue projecting pulses of the fluid only until the flame isextinguished.

It is still a further object of the invention to improve xerographicfusing apparatus by sensing the fusing zone for flames and forextinguishing any flames which may occur.

These and other objects of the present invention are achieved byapparatus including a detector in the form of an ultraviolet detectiontube positioned in the area to be sensed for flames. It is electricallycoupled to a valve to control the flow of fire extinguishing CO into thearea being sensed. The electric circuit acts to release a pulse of COupon the sensing of a flame by the detection tube. After the terminationof the pulsed flow of CO the circuit returns to its original state for asubsequent flame sensing to allow additional pulsations and sensinguntil the flame is extinguished.

For a better understanding of the invention, as well as other objectsand further features thereof, reference is had to the following detaileddescription of the invention to be read in conjunction with theaccompanying drawings, wherein:

FIG. 1 is a diagrammatic side, cross-sectional view of a xerographicmachine adapted for continuous and automatic operation embodying thefire control system of the instant invention;

FIG. 2 is a front enlarged view of the fusing source and shields viewedin the direction of arrows 22 of FIG. 1, and

FIG. 3 is a circuit diagram used in the fire control system of theinstant invention.

Shown in FIG. 1 is a xerographic machine constructed for continuous andautomatic operation and embodying the principles of the instantinvention. All of the proces sing stations referred to by letters areconventional m the xerographic art except for the fire control elementsad acent the fusing station which form the basis of the instantinvention. For the purposes of the present disclosure, the severalXerographic processing stations in the path of movement of thexerographic drum may be described as follows:

A charging station A, at which a uniform electrostatic charge isdeposited on the photoconductive layer of the xerographic drum;

An exposure station B, at which the light or radiation pattern of copyto be reproduced is projected onto the drum surface to dissipate thecharge in the exposed areas thereof to thereby form a latentelectrostatic image of the copy to be reproduced;

A development station C, at which a xerographic developing materialincluding toner powder having an electrostatic charge opposite'to thatof the latent electrostatic image, is moved into contact with the drumsurface, whereby the toner powder adheres to the latent electrostaticimage to form a xerographic powdered image in the configuration of thecopy being reproduced;

A transfer station D, at which the xerographic powdered image iselectrostatically transferred from the drum surface to a transfermaterial or a support surface;

A drum cleaning station E, at which the drum surface is brushed toremove residual toner particles remaining thereon after image transfer,and

A fusing station F, at which the toner image is permanently affixed tothe backing sheet.

For a more detailed description of this machine, reference is had to US.Patent No. 3,301,126 to Robert F.

Osborne et a1.

As shown in FIG. 1, paper which is removed from the xerographicdrum-shaped surface 10, is fed by a conveyor belt 12 toward the fusingstation F. After passing through the fuser area it moves by supplementalconveyor belt 14 into a copy catch tray 16 associating with exterior ofthe machine for collection by the operator.

In the fusing station F is a preheat roller 18 and a shielded radiantfusing element 20. These elements, insofar as they have been described,are substantially the same as that described in the aforementionedapplication to Aser et al. Located behind the reflector shield portion22 of the radiant fusing element is a second backing plate 24 shapedsimilar to the shield portion 22 of the radiant fusing element. Betweenthese two plates is a cavity 26 which functions with apertures 28 topermit the movement of a fire extinguishing fluid such as CO into thefusing area. Centrally located on the backing plate 24 is an aperturecommunicating with conduits 130 which interconnects the cavity with asupply bottle 32 of fire extinguishing fluid which is kept underpressure. A valve 34 is located on the conduits for selectivelypermitting the flow of CO from the bottles 32 to the fuser station F.The valve is adapted to be opened or closed through the action ofsolenoid SOL-1 which in turn is activated and inactivated through theaction of the contacts CR1 and CR2 of contact relay ICR. The operationof these elements is more fully described in the description of thecircuit of FIG. 3 hereinbelow.

Also located adjacent the fusing zone F is the ultraviolet detectingtube 36. This tube, which may be of the type, for example, commerciallyavailable from the Amperex Corporation under the name of AmperexElectron Tube 155 UG, is adapted to remain non-conductive during normaloperation. When it is subjected to a source of ultraviolet radiation,however, it turns conductive. It is this type of a device physicallylocated Within the area being sensed and electrically coupled to thecircuit which controls the solenoid and operation of the valve 34 thatpermits the flow of fire extinguishing fluid into the area being sensedupon the detection of a flame.

The circuit for effecting the proper timed operation of the fireextinguishing fluid is shown in FIG. 3. As explained above, the circuitis adapted to actuate the solenoid SOL-1 to open and close valve 34 toget a pulsated flow of CO from the supply bottle 32 through conduits 30to the fuser area being sensed.

Solenoid SOL1 is actuated through control relay 1CR. This relay hasthree contacts CR-l, CR-Z and (ZR-3. CR-l is a normally closed contactwhich, when open, holds CR-Z closed. CR-l is normally held closed duringthe conventional operation of the xerographic machine. But when a flameis detected in the fuser area, the control relay 1CR reverses thecondition of the contacts to permit the opening of CR1 to therebyactuate the solenoid SOL-1, open the valve 26 and consequently permitthe flow of CO to extinguish the flame. After a predetermined time offlow of CO the control relay 1CR is released to return its contacts toits first or original position and thus deenergize SOL-1, close valve 34and consequently terminate the flow of CO With the circuit in itsoriginal state, a resensing of the fuser area for the continued presenceof a flame is made. If a flame is still present, it is detected and asupplemental discharge of CO is made in the manner described above. Thiscontinues until, and only until, the flame is extinguished.

It should be pointed out here that the existence of a flame isinvariably accompanied by a stoppage of normal paper flow through thefuser area. This stoppage acts to terminate the paper feeding and otherxerographic machine functions in the manner set forth in copending US.Patent application 585,972 filed Oct. 11, 1966 in the name of LarryWood.

The instant circuit is composed of five major sections as shown in FIG.3 and designated generally as 44, 46, 48, 50, and 52. The first area 44is the power generating section which converts the standard volt ACinput into the proper DC wave shape and determines the maximum peak DC.This is necessary to operate the rest of the circuit and control theminor time delay section 48, to be later described.

Section 46 is the fire extinguishing actuation section which includesrelay contacts CR-l and CR-3 which trip SOL-1 and consequently controlsthe opening of valve 34 for permitting the flow of CO CR-3 is opened andclosed when the relay 1CR is tripped between its two positions. Theopening and closing of CR-3, in turn, activates solenoid SOL-1 to openand close valve 34 and flow the fire extinguishing fluid. This sectionalso includes the UV detector 36 also shown in FIG. 1, but which acts inthis capacity as a functioning part of the circuit. The above mentionedminor delay section is noted as 48. This circuit section prohibits minorUV detections by detector 36 from tripping the control relay lCR. Suchminor UV detection might be caused by random photon excitations in theform of cosmic radiation in proximity to the detector 36. Theseexcitations are generally in the order of a few milliseconds and it isnot desired to flow the CO into the fuser area upon their presence.Consequently, this section acts, in conjunction with the powergenerating section 44 to filter out the effects of UV photon excitationsin the fuser area. This section, thus only allows extended UVexcitations, longer than a few milliseconds, as would be caused by aflame, to trip the control relay CR1. This section thus only operateswhen the UV presence exceeds an extended duration of time, as forexample, in the order of 50 milliseconds.

The fourth section of the control circuit 50 is the relay actuatingsection and includes the contact relay l-CR. This section also includessilicon controlled rectifiers Q3 and Q4, or similar threshold switchingmeans, one of which must always be conducting when the circuit is in itssecond or CO dispensing state. The conducting of one or the other of thecontrolled rectifiers acts to hold the relay in its second position toreverse its contact and consequently permit the flowing of CO The finalsection of the circuit is the major timing section 52. This circuitsection is operational only after a fire has been detected and the COemployed for extinguishing it. This circuit section acts when energizedto return the circuit to its original or first state after apredetermined pulsation of CO as for example, three seconds.

When the circuit of the instant invention is rendered operative throughthe application of suitable power through lines 38 and 40, only thepower generating section 44 is carrying current. This is becausedetector 36 is non-conductive due to the absence of UV detection.Consequently, no power is brought into the fire extinguisher actuationsection 46, minor time delay section 48, or control circuit section 50.In like manner, at this time, relay contact CR2 is open prohibiting theflow of power into the major time delay section 52 of the circuit.Current normally attempts to flow through the control circuit section 50including the contact relay 1CR and SCR Q3 and Q4. However, there is nopower on the gates of these SCRs and consequently they act to renderthis portion of the circuit open to prohibit a current flow through therelay.

When, however, an extended presence is detected by detection tube 36,the circuit is closed through this portion of the circuit to bring acurrent through amplifying transistors Q1 and Q2 to thereby activate thegate of SCR Q3 and permit a flow of current through the contact relay1CR. This tripping of the relay reverses the state of the relay contactsCR1, CR2 and CR3. With contact CR1 open, no further current can go tothe gate of Q3 since this portion of the circuit is now open. However,the opening of contact CR1 is accompanied by a closing of contact CR-2to bring power through the major time delay section 52 of the circuit.This acts to energize the gate of this CR Q4 to render Q4 conducting andpermit the continuance of the current flow through relay 1-CR. When thetime constant for the major time delay section of the circuit has beenreached, all power will flow into the gate of SCR Q5 to render thatportion of the circuit conducting to thereby short out the power to thegate of SCR Q4. When this occurs the gates of Q3 and Q4 have each beenrendered inoperative to thereby cause the stoppage of current flowthrough the relay. This returns the circuit to its original state byclosing CR1 and opening CR2.

The use of capacitor C2 in parallel with resistor R8 allows for minor UVdetections by bulb 36 from energizing the gate of Q3 at an undesirabletime. Capacitor C2 is chosen so that minor energization of this leg ofthe circuit will bleed 011 short conductances of tube 36 as may becaused by random photon excitations.

More specifically, the instant circuit is rendered operationalsimultaneously with the activation of the xerographic reproducingmachines in which it is to be operated. Power enters the circuit throughlines 38 and 40. Line 42 is a common ground. The power acts to bring thecircuit into its first state where it is ready to sense a fire in thefusing area. Line 38, in conjunction with ground line 32, brings powerthrough diode D1 which gives a preliminary rectification to the 110 voltAC of the power input line. Diode D1 and resistor R1 are positioned inseries with three parallel circuit lines. Of these three parallelcircuit lines, the first contains a capacitor C1, the'second a resistorR2, and the third a gang of three Zener diodes, D2, D3 and D4. In thepreferred embodiment, D2 and D3 and D4 are substantially of equal valueand act together to determine the maximum or peak DC voltage to beobtained. R1, C1, and R2 determine the wave shape output. A sawtoothwave is desired to permit effective operation of the minor time delayportion of the circuit and proper tube operation. Power is in thisportion of the circuit during all time portions of machine operation,when a flame is to be sensed. Further flow of power is prohibited bynon-conducting detector tube 36 and open relay contact CR2.

Located in series with resistor R1 on line is the UV detector 36 and thenormally closed contact CR1 of r lay 1-CR. CR1 is held closed as aresult of 1-CR not being energized while the detector is not respondingto the presence of a flame. Resistors R3 and R4 are in series with thedetector and contact CR1. R3 and R4 are separated by a lead into Q1, Q3for proper power input into the transistor Q1 and supplemental portionsof the circuit.

When the detector 36 becomes conductive due to the presence ofultraviolet in its vicinity and with power being supplied thereto,transistors Q1 and Q2 act as an amplifier to charge capacitor C2 throughresistor R7. When C2 becomes charged to a sufiicient voltage the siliconcontrolled rectifier Q3 conducts power through relay -1CR to therebyreverse its orientation and perimit contact CR1 to open and the CO toextinguish a flame. When the detector 36 does not sense UV, it remainsnon-conducting and the DC voltageremains below this conducting valuebecause capacitor C2 discharges through resistor R8. But with extendedUV present, i.e., a flame being detected, C2 becomes sufiicientlycharged to turn on the silicon controlled rectifier Q3 to energize lCRand fire this portion of the circuit.

Diode D5 rectifies the AC input to relay ICR from line 40. Resistor R9in series with diode D5 acts to limit the initial surge of power intothe SCR Q3 during operation. Located between Q3 and R9 in parallel withone another are capacitors C3 and the contact relay 1CR. C3

functions to hold in the relay during negative half cycles of current.Zener diode D6 raises the voltage level required to permit firing of SCRQ3 to thus assist in prohibiting minor time delays from switching therelay. With sufliciently long conduction by detector 28, power throughQ3 is conducted, tripping the relay 1-CR, CR3 and SOL-1, and activatingthe major timing section of the circuit. Thyrector D9 couples the relayactuating section with the return line or ground 42. D9 functions toremove the efiect of transients or spikes from the system in theconventional fashion.

With the relay CR1 tripped, Q3 is rendered inactivated while Q4 isrendered conductive to actuate the major time portion of the circuit.This is because closed contact CR2 brings power to this portion of thecircuit. Diode D7 is in series with parallel resistors R11 and R12.These elements are in series with parallel combination of Zener diode D8and capacitor C5. This combination provides a constant DC voltage fromline 38 when this portion is energized.

Normally open contact CR2 links this voltage shaping section of thecircuit with the uni-junction timing circuit. The uni-junction timingcircuit includes uni-junction transistor Q6 which functions inconjunction with resistors R16, R17, R18, R19 and R20 as well ascapacitors C4 to permit the retention of this portion of the circuitoperative for the desired time, as for example, three seconds. This timecan be varied easily since resistor R20 is variable. As can beunderstood, this portion of the circuit can only be energized throughthe closing of CR2 and CR3 along with the tripping of SOL-1 which iseffected by the switching of relay ICR.

Under normal conditions, the gates of SCR Q3 and Q4 would tend to remainenergized after intial energization. But in the instant circuit, diodeD5 passes half-wave rectified current through relay 1CR and the SCRswhich allow the forward potential on the anode end of the SCRs to go tozero. Thus when the current through Q3 and Q4 goes to zero with no poweron the gates, the SCRs return to a non-conducting or blocking state.

Serially located resistors R13, R14 and R15 represent a biasing circuitto permit energization of SCR Q4 after the energization of relay 'ICR.SCR Q5 becomes activated by the timing circuit to short the biasingcircuit of Q4 after the elapse of the three second timed interval. Thisshorting acts to terminate the conduction of SCR Q4 to permit, inconjunction with the previous inactivation of 7 SCR Q3, the return ofthe contact relay 1CR and the entire circuit to its original state.Supplemental sensings by the detector 36 in the above-described fashioncontinue until the flame is extinguished.

It can thus be seen that the disclosed embodiment defines a system forcontrolling fires in a xerographic fusing zone. It is a dependablesystem, quickly responsive to the occurrence of flames and effective forthe control thereof.

While the present invention, as to its objects and advantages, has beendescribed herein as carried out in a specific embodiment thereof, it isnot desired to be limited thereby; but it is intended to cover theinvention broadly within the scope of the appended claims.

What is claimed is: 1. Fire control apparatus comprising, incombination, flame sensing means positionable in an area to becontrolled for flames, said flame sensing means including a bulb havingan electrically non-conducting capacity under normal conditions buthaving an electrically conducting capacity when exposed to ultravioletconditions,

conduit means linking the area to be controlled with a supply of fireextinguishing fluid,

valve means to selectively open and close the conduit means to permit orprohibit the flow of fire extinguishing fluid to the area to becontrolled and control means coupling the flame sensing means and thevalve means to permit the flow of a predetermined pulse of fireextinguishing fluid upon the detection of a flame by the flame sensingmeans, said control means also including minor time delay elements toretain the valve means closed during exposure of the flame sensing meansto short duration ultraviolet conditions as caused by cosmic radiation.

2. Fire control apparatus comprising, in combination,

flame sensing means positionable in an area to be controlled for flames,conduit means linking the area to be controlled with a supply of fireextinguishing fluid,

valve means to selectively open and close the conduit means to permit orprohibit the flow of fire extinguishing fluid to the area to becontrolled and control means coupling the flame sensing means and thevalve means to permit the flow of a predetermined pulse of fireextinguishing fluid upon the detection of a. flame by the flame sensingmeans, said control means including major time delay elements to returnthe control means to its initial flame sensing condition after apredetermined timed flowing of fire extinguishing fluid caused by thedetection of a flame.

3. The apparatus as set forth in claim 2 wherein said control meansfurther includes a control relay having a first and second thresholdswitching means in parallel to each other and coupled to one terminal ofthe control relay with the gate of the first of said threshold switchingmeans coupled to said flame sensing means for energization thereby totrip said relay and open said valve in response to flame detection, andwith the gate of said second threshold switching being coupled to saidmajor time delay elements for energization thereby to retain said relayand said valve open until the elapse of a predetermined time whereuponthe gate of said threshold switching means is deenergized to return saidrelay and said valve to their original states.

4. For use adjacent a xerographic fusing zone, apparatus to controlunwanted flames therein comprising:

8 an ultraviolet flame detecting tube which is normally non-conductiveduring the absence of ultraviolet radiation and conductive during thepresence of ultraviolet radiation as caused by a flame,

conduit means linking the fusing zone with a supply of fireextinguishing fluid,

a valve in the conduit means selectively operable in a first positionwherein the conduit is closed to prohibit a flow of fire-extinguishingfluid into the fusing zone and operable in a second position wherein thevalve is open to permit a flow of fire extinguishing fluid to the fusingzone,

circuit means coupling the valve and the detecting tube,

said circuit means being normally held in a first state during theabsence of ultraviolet radiation to retain the valve in its first orclosed position,

said circuit means being activated into a second state upon theconduction of said detecting tube as caused by the ultraviolet radiationof the flame in the fusing zone to switch the valve into its secondstate for causing a flow of fire extinguishing fluid into the fusingzone,

said circuit means also including a major time delay portion to returnthe circuit to its first state after a predetermined time pulsation offire extinguishing fluid whereby said circuit terminates the flow offire extinguishing fluid and is then again operative to resense thefusing zone for continued ultraviolet radiation of the flame.

5. The apparatus as set forth in claim 4 wherein said circuit means alsoincluding a minor time delay portion to render said circuit inoperativeto switch from its first state to its second state upon the detection ofextremely short pulses of ultraviolet radiation as caused by cosmicradiation.

6. Fire control apparatus including,

flame sensing means responsive to ultraviolet radiation and positionedin an area to be sensed,

conduit means linking the area to be sensed with a supply of fireextinguishing fluid,

valve means to selectively open and close said conduit means to permitor prohibit the flow of fire extinguishing fluid to the area to besensed, control means coupling said flame sensing means and said valvemeans to permit the flow of fire extinguishing fluid upon the detectionof ultraviolet radiation from a flame by said flame sensing means andmeans to render said flame sensing means incapable of actuating saidcontrol means upon the detection of ultraviolet radiation of shortdurations.

7. The apparatus as set forth in claim 6 and further including means toreturn said valve means to a state prohibiting the flow of fireextinguishing fluid after a predetermined quantity of fire extinguishingfluid has flowed to the area to be sensed.

References Cited UNITED STATES PATENTS 3,154,724 10/1964 Giufirida.340--228.2 X 3,163,108 12/1964 Hornberger et al. 1692 X 3,339,624 9/1967Cowgill 1692 X ALLEN N. KNOWLES, Primary Examiner US. Cl. X.R. 169-19

